最小生成树之Prim算法+堆优化

#include<bits/stdc++.h>
#define INF 0x3f3f3f3f3f3f3f3f
#define mod 1000000007
#define IOS ios::sync_with_stdio(false)
#define endl '\n'
using namespace std;
typedef long long ll;
const int maxn = 1e5 + 10;
typedef pair<int, int> p;
vector<p>vec[maxn];
int vis[maxn];
int main() {
  int n, m;
  int u, v, val;
  int ans = 0;
  scanf("%d%d", &n, &m);
  memset(vis, 0, sizeof(vis));
  for (int i = 1;i <= m;++i) {
    scanf("%d%d%d", &u, &v, &val);//读入边
    vec[u].push_back(p(val, v));//顶点u到v距离为val
    vec[v].push_back(p(val, u));//顶点v到u距离为val
  }
  priority_queue<p, vector<p>, greater<p> >pq;//优先队列
  vis[1] = 1;
  for (int i = 0;i < vec[1].size();++i) {
    pq.push(vec[1][i]);//将与1相连的顶点入队
  }
  while (!pq.empty()) {
    p now = pq.top();
    pq.pop();
    if (!vis[now.second]) {//当前顶点没有被访问过
      vis[now.second] = 1;//标记已经被访问过
      ans += now.first;
    }
    for (int i = 0;i < vec[now.second].size();++i) {//枚举与刚刚进树的这个顶点
      if (!vis[vec[now.second][i].second]) {//相邻的顶点
        pq.push(vec[now.second][i]);//将其进队列 优先队列会自动排序
      }
    }
  }
  printf("%d\n", ans);
  return 0;
}